CN101253403B - sensing device - Google Patents

Abstract

The present invention provides a sensing apparatus for obtaining information of a test specimen using an electromagnetic wave including a frequency region within a frequency region of 30GHz to 30THz, the sensing apparatus comprising: an electromagnetic wave transmitting section including a plurality of transmission sections (4a, 4b) for propagating an electromagnetic wave; and a detection section (3a, 3c) for receiving and detecting the electromagnetic wave from the plurality of transmission sections (4a, 4b), wherein at least one of the plurality of transmission sections (4a, 4b) is constructed so that the test specimen (5, 6) can be placed in a portion affected by the electromagnetic wave propagating therethrough.

Description

sensing device

technical field

The present invention relates to a sensing device and method for obtaining information such as characteristics of a target test specimen by using electromagnetic waves including a frequency region mainly in the millimeter wave to terahertz wave region (30 GHz to 30 THz).

Background technique

In recent years, non-destructive sensing technology using electromagnetic waves at millimeter wave to terahertz (THz) wave frequencies (30 GHz to 30 THz) has been under development. An example of a technique currently being developed in the field of application of electromagnetic waves of such a frequency band is an imaging technique using a safety fluoroscope device instead of an X-ray fluoroscope. In addition, examples of techniques now being developed include spectroscopic techniques for obtaining absorption spectra or complex permittivity of materials to examine bonding states therein, techniques for analyzing biomolecules, and techniques for estimating carrier concentration or mobility techniques.

Until now, a photoconductive device including an antenna that also serves as an electrode, the antenna being provided on a photoconductive film formed on on the substrate. Fig. 8 shows a structural example of a photoconductive device. The substrate 130 has, for example, a silicon-on-sapphire structure treated with radiation. In the substrate 130, a silicon film as a photoconductive material is formed on a sapphire substrate. An LT-GaAs film grown on a GaAs substrate at a low temperature is used as a photoconductive film in many cases. The dipole antenna 138 formed in the substrate surface includes a pair of dipole feeders 138a and 138b and a pair of dipole arms 139a and 139b. The light pulses converge on the gap 133 . When a voltage is applied across the gap 133, a THz pulse is generated. When a photocurrent is detected without applying a voltage across the gap 133, a THz pulse can be detected. Here, the photoconductive device is the detector 132 . The photocurrent is detected by the current amplifier 134 . The substrate lens 136 has functions of: performing coupling from a slab mode (substrate mode) of electromagnetic waves confined in the substrate 130 to a radiation mode for free space; and controlling the radiation angle of the electromagnetic wave propagation mode in space.

The above structure is an example of propagating electromagnetic waves through space using a single photoconductive device. Small functional devices have also been proposed in which semiconductor thin films serving as photoconductive devices and transmission paths for propagating generated electromagnetic waves are integrated on a single substrate (see Applied Physics Letters, Vol.80, No.1, 7January, 2002 , pp.154-156). FIG. 9 is a plan view showing the functional device. The functional device has a structure 164 in which a thin film of a photoconductive device including only an LT-GaAs epitaxial layer is transferred to a part of high-frequency transmission paths 165 and 163 formed on a silicon substrate 160 . In the structure 164, a microstrip line is formed on the substrate 160 so as to sandwich an insulating resin. Creates a gap in a portion of the line. A thin film of LT-GaAs is placed just below the gap. Driving is performed so that the laser beam is emitted from the surface side of the substrate 160 to the gap interposed between the metal lines 161 and 165 through spatial propagation to propagate the generated THz electromagnetic wave onto the line. When a test sample 167 to be examined is applied to a filter region 166 with a resonant structure on the transmission path, a change in propagation conditions is detected from the section 162 using the EO crystal. Therefore, the characteristics of the test sample 167 can be checked.

However, according to the method disclosed in Applied Physics Letters, Vol.80, No.1, 7January, 2002, pp.154-156, the amount of change in the propagation condition of the terahertz wave of the test sample is small. Therefore, a larger number of test specimens is required. In order to improve sensitivity, it is necessary to increase the intensity of electromagnetic waves. When comparing a reference test sample to a target test sample, it is necessary to acquire and store data for each step, or to perform additional measurements by sensing devices with different transmission paths. In this case, it is difficult to adjust the conditions for measuring the reference test sample to the same conditions as the conditions for measuring the target test sample. Therefore, it is difficult to accurately estimate the amount of change of the target test sample from the reference test sample.

Contents of the invention

In view of the above circumstances, a sensing device according to the present invention is used to obtain information of a test specimen by using electromagnetic waves including a frequency region in the frequency region of 30 GHz to 30 THz. The sensing device includes: an electromagnetic wave transmission section having a plurality of transmission sections for propagating electromagnetic waves therethrough; and a detection section for receiving and detecting electromagnetic waves from the transmission sections. In this case, at least one of the plurality of transmission parts is configured such that a test sample can be placed in a part which is influenced by electromagnetic waves propagating therethrough.

In view of the foregoing, a sensing method according to an aspect of the present invention allows sensing to obtain information of the test specimen by using the sensing device. The sensing method includes: a detection step of detecting, by a detection part, electromagnetic waves propagating through the respective transmission parts in a case where a test sample is placed in at least one of the transmission parts of the electromagnetic wave transmission part; and In the step of processing the signal from the detection part in the detection step to obtain the information of the test sample. In the sensing method, the detecting step may be a step in which a test sample is placed in one of the transfer parts and a reference test sample is placed in the transfer part In the case of another one of , the electromagnetic wave propagating through each part is detected by the detection part, and thereafter a differential output is detected based on the signal from the detection part in the detecting step to measure the kind of characteristics.

According to the present invention, there are a plurality of transmission sections for separately propagating electromagnetic waves including information on a test sample to be measured and electromagnetic waves including information other than information on the test sample. Therefore, a plurality of detection signals can be obtained substantially simultaneously. Accordingly, the detection signal is properly processed (for example, comparison calculation is performed), so that information on the characteristics of the test sample and the like can be obtained with high sensitivity and at a relatively high speed.

Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or like parts throughout.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the embodiments of the invention and together with the description serve to explain the principles of the invention.

1 is a perspective view illustrating a sensing device according to an embodiment and Example 1 of the present invention;

FIG. 2 is a graph showing an example of an output waveform from the sensing device shown in FIG. 1;

3 is a plan view showing a sensing device according to Example 2 of the present invention;

4 is a plan view showing a sensing device according to Example 3 of the present invention;

5 is a perspective view showing a sensing device according to Example 4 of the present invention;

6 is a block diagram showing a sensing device according to Example 5 of the present invention;

7 is a block diagram showing a sensing device according to Example 6 of the present invention;

FIG. 8 shows an example of a conventional terahertz generation unit; and

FIG. 9 shows a conventional example of a terahertz transmission path.

Detailed ways

An embodiment of the present invention will be described with reference to FIG. 1 . What is realized here is a sensing device provided with a plurality of transmission paths through which terahertz waves are mainly propagated as electromagnetic waves, thereby detecting a test sample and a reference test sample substantially simultaneously, And the results obtained by comparing among them are directly output, thereby achieving improved sensitivity.

FIG. 1 is a perspective view showing a chip portion of a sensing device. In FIG. 1 , transmission paths 4 a and 4 b are formed on the chip surface of a substrate 1 . The portion generating the terahertz wave is a photoconductive switching element formed in a region to which the low-temperature-grown (LT-)GaAs thin film 3b is transferred. The electromagnetic waves generated here propagate in opposite directions through the two transmission paths (transmission sections of the electromagnetic wave transmission section) 4a and 4b. Terahertz waves are generated by emitting an ultrashort pulse laser beam from a titanium sapphire laser 10 to the LT-GaAs thin film 3b to which an electric field is applied. The generated terahertz waves are emitted in all directions so that the output in the case where the two transmission paths 4a and 4b are provided does not become smaller than the output in the case where a single transmission path is provided. Therefore, energy usage efficiency is improved compared to the conventional example described in Applied Physics Letters, Vol.80, No.1, 7 January, 2002, pp.154-156. When the generating source (electromagnetic wave generating section) is placed at the center of the linear transmission path, the loss of electromagnetic waves is small, so that the efficiency becomes extremely high. In this embodiment, such a structure is used.

Electromagnetic waves propagating in various directions are detected by two LT-GaAs photoconductive switches formed in the regions to which the LT-GaAs thin films 3a and 3c are transferred, similar to the electromagnetic wave generation section middle. Amplifiers 8a and 8b convert the respective output currents from the switches into voltages, after which a comparator device 9 calculates the difference between the outputs from amplifiers 8a and 8b. Therefore, the common phase noise can be eliminated, so that the difference between the test samples 5 and 6 applied to the transmission paths 4a and 4b can be detected with high sensitivity. Test samples 5 and 6 were placed in portions affected by electromagnetic waves propagating through the transmission path.

When one of the test specimens 5 and 6 is placed as a reference test specimen, a slight difference between the reference test specimen and the test specimen to be measured can be obtained. That is, a reference test sample is placed on at least one of the transport paths. A signal is detected by a detection section different from that of a test sample to be inspected, and thereafter, an output is obtained by comparison among a plurality of signals, so that minute changes can be obtained with high sensitivity. Therefore, very small quantities of test specimens can be accurately measured. The reference test sample and the test sample are inspected simultaneously, so that high-speed inspection can be performed.

As described above, in this embodiment, a plurality of transfer paths and detection sections corresponding thereto are provided on the same substrate. Suitable for use as the transmission path are microstrip lines, coplanar lines, coplanar strip lines, or individual lines that may be formed on the surface of the substrate. A transmission path configuration suitable for use is a shape in which the transmission path extends linearly in both directions from the generating source, or a transmission path configuration suitable for use is of a type in which the transmission path is Y-branched at one point thereof ,etc. When three or more transmission paths are used, the transmission paths may extend radially from the generation source. In this case, for example, a test specimen is placed on one transport, a reference test specimen is placed on the other transport and no test specimen is placed on the other transport. With this configuration, electromagnetic waves can be detected from the respective transmission sections. In this embodiment, the electromagnetic wave transmitting section includes a plurality of separate transmission paths. The electromagnetic wave transmitting section may also include a plurality of transmission paths having a common portion (see the example shown in FIG. 3 ) or a plurality of space portions separated from each other or having a common portion (see the examples shown in FIGS. 6 and 7 ).

The electromagnetic wave generating section coupled to the transmission path may be placed outside the same substrate or integrated on the same substrate. A system may be employed: a system in which electromagnetic waves are distributed from a single generation section to a plurality of transmission paths, or a system in which a plurality of generation sections corresponding to transmission paths may be provided. It is preferable that the electromagnetic waves propagated from the generation section to the respective transmission sections of the electromagnetic wave transmission section are correlated with each other and have a coherent characteristic. In addition to photoconductive switching elements for generating terahertz pulses in response to externally applied femtosecond laser beams, options for the generating section include, for example, resonant tunneling diodes or quantum cascade lasers, which can be activated by current injection. oscillation. When lasers are used, detector options include photoconductive switching elements. When performing current injection, detector options include, for example, Schottky barrier diodes.

Devices for placing test specimens include devices that simply apply to a surface with an inkjet or the like, and devices that have a flow path for providing liquid into the vicinity of a transfer path.

As mentioned above, two or more transports are set to different states (that is, different test specimens are placed on multiple transports respectively, while there may be a situation where nothing is placed on one of the transports). Case). The detection section detects electromagnetic waves from the respective transmission sections substantially simultaneously. The detection signal is suitably processed (for example, comparison calculations are performed), thereby obtaining information on the characteristics of the test specimen, etc., with high sensitivity and relatively high speed. Therefore, terahertz sensing can be performed. In contrast, conventionally, the test sample has to be measured separately.

[example]

Hereinafter, specific examples will be described.

(Example 1)

Example 1 will be described with reference to FIG. 1 . In FIG. 1 , a metal conductor layer 15 which becomes a ground plane and a dielectric 2 are formed on a silicon substrate 1 . LT-GaAs films 3 a to 3 c each having a thickness of approximately 2 μm and metal wirings 4 a , 4 b , 7 a , and 7 b are formed on dielectric 2 . For example, a Ti/Au layer can be used as metal conductor layer 15 , and BCB (product name: Cycloten) having a thickness of 5 μm can be used as dielectric 2 . The present invention is not limited thereto.

LT-GaAs films 3a to 3c were obtained as follows. A sacrificial layer of AlAs is grown on a GaAs substrate by the MBE method, and thereafter GaAs is grown at a low temperature of approximately 250°C. The grown GaAs film is lifted from the AlAs layer and can thus be bonded to the BCB dielectric 2 . When only the LT-GaAs film 3b of the transferred LT-GaAs film is to be electrically connected to the ground plane 15, via wiring (not shown) is formed. A voltage from a power source 16 may be applied between the metal wiring 4a and the ground plane 15, and between the metal wiring 4b and the ground plane 15 to apply an electric field vertically to the LT-GaAs film 3b. Each of the metal wirings 4 a and 4 b has a width of 5 μm and a length of 1 mm, and is made of Ti/Au. Metal wirings 4a and 4b constitute a microstrip line together with ground plane 15, and serve as a transmission path for electromagnetic waves generated in LT-GaAs film 3b. In addition to microstrip lines, the transmission path can be a coplanar line or a single line. A gap having a width of approximately 5 μm is formed on the surface of each of the LT-GaAs films 3 a and 3 c between the wirings 4 a and 7 a and between the wirings 4 b and 7 b to constitute a photoconductive switching element.

When a sensing device is used, the targeted test specimens 5 and 6 are applied to the respective transport paths 4a and 4b by ink jetting or the like in controlled quantities and at controlled positions. The propagation condition of the electromagnetic wave changes according to the presence of the test specimen. The peak value of the terahertz pulse generated from the photoconductive switching element formed in the LT-GaAs film 3b decreases, its delay time changes, and its waveform changes, so that the characteristics of the test sample and the like can be measured. For example, a current-voltage conversion amplifier such as a transconductance amplifier can be used as each of the amplifiers 8a and 8b. A differential amplifier can be used as comparator device 9 .

Next, the operation of the entire sensing device will be described. While an electric field of 2V is applied to the LT-GaAs film 3b by the power source 16, a part of the output of the titanium sapphire laser 10 having a pulse width of approximately 100 femtoseconds is applied to the LT-GaAs film 3b to generate a terahertz wave pulse. The remaining part of the output passes through the retardation optical system 11, and is distributed to the LT-GaAs films 3a and 3c. Timings at which terahertz wave pulses are applied to LT-GaAs films 3a and 3c are preferably adjusted in advance by the optical system so that they coincide with each other by correcting delay times caused by manufacturing errors of transmission paths 4a and 4b. In order to adjust the timing, it is only necessary to scan the delay optical system 11 under the condition that the test samples 5 and 6 do not exist so that the differential output of the differential amplifier 9 becomes 0. This corresponds to adjustment means for detecting in advance the difference between the delay times of electromagnetic waves propagating through the transmission paths in the initial state, and for correcting the difference between the times of electromagnetic waves propagating through the respective transmission paths based on the detected information. In the initial state, there is no test specimen in contact with the transport path and the reference test specimen. Therefore, accuracy is improved when differences in propagation conditions (such as delay times) suitable for sensing devices are corrected in advance.

The signal from the differential amplifier 9 is pre-stored in case the reference test sample is placed on only one of the transmission paths. Furthermore, the signal from the differential amplifier 9 in the absence of the test sample is compared with the signal from the differential amplifier 9 in the presence of the test sample. Therefore, accuracy can be further improved.

FIG. 2 shows an example of a waveform output from the differential amplifier 9 in the case of using a DNA sample as a test sample. In this case, the test sample 5 has a double-stranded structure in which single-stranded DNA is applied to the transfer path 4a so as to have a 200 μm , and the target DNA is further applied thereto to achieve hybridization. On the other hand, Test Sample 6 is a single-stranded reference test sample in which the same single-stranded DNA was applied to the transfer path 4b and no reaction was performed. The double-chain structure has different delay times, so that the waveform shown in Figure 2 can be obtained as its differential output. The delay time difference is small, so that an oscillation structure and the like are necessary in the prior art. However, a simple structure is used to obtain a signal when a differential output is detected. As described above, when the signal obtained with the test sample placed on only one of the transmission paths is stored in advance, two original waveforms can be estimated from the differential output to perform Fourier analysis. When a specific fingerprint spectrum is located in the terahertz wave region, the spectrum can be detected. Waveform analysis is difficult to perform when there is a resonant structure as described in AppliedPhysics Letters, Vol.80, No.1, 7 January, 2002, pp.154-156.

The above describes the case where one type of test sample is measured using a chip. When a chip in which a plurality of transmission paths are arranged in an array on the same substrate 1 is scanned appropriately to apply a titanium sapphire laser beam to a desired position of a generation section, various types of test samples can be measured using the chip. Even in this case, high-speed measurement is possible.

(Example 2)

The operation in Example 2 of the present invention is basically the same as that in Example 1. The difference is that the metal wiring 22 is branched at one point thereof to form Y-branch transmission paths 27a and 27b, as shown in the plan view of FIG. 3 . A laser beam is applied to a gap portion between the wirings 22 and 23 at the generating section 21 a. The laser beam may be an ultrashort pulsed laser beam of approximately 100 femtoseconds, as is the case in Example 1. A THz-order oscillation frequency difference can be generated between two semiconductor lasers oscillating in the 830nm band, and a single-frequency THz continuous wave can be applied as the beat signal.

The terahertz wave from the generation unit 21a is divided into two waves by the Y-branch transmission paths 27a and 27b. These two waves reach detection regions 21b and 21c where photoconductive switching elements are formed to perform signal detection. At this time, balanced reception using the differential amplifier 26 is performed for signal reception output. As in the case of Example 1, when the reference test sample 25a and the test sample 25b are applied to, for example, the positions shown in the figure, the sensitivity can be improved. Unlike Example 1, the terahertz wave is divided so that the signal strength is reduced. However, the detection areas 21b and 21c can be placed close to each other, and the test specimens 25a and 25b can be placed close to each other, thereby suppressing errors caused by variations in the positions of the respective parts. In FIG. 3 , reference numeral 20 denotes a substrate, and reference numeral 24 denotes wiring, which has the same function as that of each of the wirings 7 a and 7 b described in Example 1.

(Example 3)

Example 3 of the present invention uses current injection into a terahertz oscillator element. Unlike the above-mentioned examples, no external laser beam needs to be applied, which can significantly reduce the size of the sensing device. No optical adjustment mechanism is required, which reduces costs. Fig. 4 is a plan view showing a terahertz oscillator element. In this example, the transmission paths are formed as coplanar strip lines 41 and 42 having two lines provided on the surface of the substrate 40 . Each of the lines 41 and 42 has a distributed Bragg reflector (DBR) structure to resonate at a specific frequency, and also serves as a resonator of the oscillator 43 . The oscillator 43 is designed in such a way that a resonant tunneling diode (RTD) is used for the gain structure and the maximum gain peak is obtained around 1 THz. Therefore, even in the case of DBR, a diffraction grating is formed so that reflection intensity becomes stronger in the vicinity of 1 THz. The electromagnetic wave oscillated by the current injected into the oscillator 43 reaches the detectors 44 and 45 . For the gain structure, a quantum cascade laser or the like can be used. In this example, detectors 44 and 45 each comprise planar Schottky diodes. The generated photocurrent corresponding to the intensity of the arriving electromagnetic wave is amplified by current amplifiers 46 and 47 . The differential output is obtained by a differential amplifier 48 .

In this example instead of pulses a continuous wave is used so that the output of detectors 44 and 45 reflects the intensity of the incoming continuous wave. In this structure, when a sample is placed on the transmission paths 41 and 42, the selected wavelength and the reflection coefficient of the DBR are changed with the change of the dielectric constant, thereby changing the oscillation state of the oscillator 43. Furthermore, the ratio between the intensities of the electromagnetic waves output to the detectors 44 and 45 is changed by the difference between the two test samples. Therefore, the characteristics and the like of the test sample can be measured with high sensitivity.

This example is particularly effective when the frequencies at which the interference with the test specimen is large is known and the presence or absence of the test specimen is detected.

(Example 4)

In a structure according to each of the above examples, a test coupon is applied to the surface of the substrate. A flow path capable of continuously performing supply and discharge of test specimens at high speed may be used. In Example 4, as shown in FIG. 5 , the basic structure is the same as that in Example 1. Flow paths 51 and 52 are additionally provided orthogonally to the microstrip lines 4a and 4b so that test samples can be supplied thereto. In FIG. 5 , except for the portion of FIG. 5 , the reference numerals and descriptions of the same constituent parts as those shown in FIG. 1 are omitted here.

In this example, at the time of inspection, a sample is supplied through the flow paths 51 and 52, after which measurement is performed. After the measurement is completed, the test sample can be discharged from the flow paths 51 and 52 by pushing the test sample. In this case, the test sample can be drained by suction.

The laser beam application operation, the signal detection operation, and the like are performed as in Example 1. In this example, the test coupons can be changed at high speed. Therefore, a single sensing device is used to measure a plurality of test samples while changing the test samples, so that the measurement time can be shortened.

(Example 5)

An electromagnetic wave transmission section including a plurality of transmission sections for propagating electromagnetic waves through the plurality of transmission sections may include a plurality of spaces. FIG. 6 shows an example in which the electromagnetic wave transmitting section includes a first space portion 61 a and a second space portion 61 b having a part of the common portion 60 . The electromagnetic wave from the generating section 62 for generating electromagnetic waves is divided into two waves by the wave splitter 63 . One of the two waves propagates through the first space portion 61a, and is detected by the first detection section 64a. The other of the two waves propagates through the second space portion 61b by the mirror 65, and is detected by the second detection section 64b. At this time, the reference test sample 66a is placed in the common space portion 60 between the generating part 62 and the wave splitter 63, and the test sample 66b is placed in a second space portion between the wave splitter 63 and the reflector 65. 61b. Even in such a structure, when the difference between the outputs from the detection sections 64a and 64b is calculated by the comparator device 67, the same effect is obtained based on the same principle as in each of the above examples.

(Example 6)

As shown in FIG. 7, the electromagnetic wave transmitting part may include a first space part 71a and a second space part 71b which are separately placed. In Fig. 7, reference numeral 72 represents a generating part for generating electromagnetic waves, reference numeral 73 represents a wave splitter, reference numerals 74a and 74b represent a first detection part and a second detection part respectively, reference numeral 75 represents a reflecting mirror, and reference numeral 76a represents a reference test Sample, reference numeral 76b designates a test sample, reference numeral 77 designates a comparator device. Even in such a configuration, when the difference between the outputs from the detection sections 74a and 74b is calculated by the comparator device 77, the same effect is obtained based on the same principle as in the configuration example shown in FIG.

Since many apparently widely different embodiments of the invention can be made without departing from the spirit and scope of the invention, it should be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.

This application claims priority from Japanese Patent Application No. 2005-248561 filed on Aug. 30, 2005, which is hereby incorporated by reference in its entirety.

Claims (2)

1. A sensing device for obtaining information of a test specimen using electromagnetic waves including a frequency region in the frequency region of 30 GHz to 30 THz, the sensing device comprising: Substrate; a generating section provided on the substrate for generating electromagnetic waves; a plurality of transmission parts provided on the substrate for propagating electromagnetic waves generated by the generation part; and a detection section for detecting electromagnetic waves from the plurality of transmission sections, providing the plurality of transmission parts and the detection parts corresponding thereto on the same substrate, wherein at least one of said plurality of transport parts is constructed such that a sample can be placed, Wherein, one of the plurality of transmission sections is a transmission section in which a sample is set and the condition of electromagnetic waves propagating therethrough is changed, and the other of the plurality of transmission sections is a transmission section that transmits section in which the reference sample is set and the condition of the electromagnetic wave propagating through it is changed, wherein the characteristic of the sample is measured based on an output obtained by comparison between signals from the detection section that detects an electromagnetic wave propagating through a transmission section in which the sample is set ; and electromagnetic waves propagating through the transmission section in which the reference sample is disposed, and wherein the sensing device further includes: adjusting means for correcting a difference in delay time of electromagnetic waves propagating through the plurality of transmission parts based on information on a difference between delay times of electromagnetic waves propagating through the respective transmission parts, in The difference is detected in advance in a state where there are no samples to be placed in the plurality of transfer sections and a reference sample. 2. The sensing device of claim 1, wherein the plurality of transmission sections are positioned to sandwich the generation section along a line passing therethrough.

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